Northern red oak (NRO), Quercus rubra L., is a valuable tree species for timber, wildlife, restoration, and urban forestry. Seed production and growth responses from different maternal sources can be widely variable. Rooting choice stem cuttings of NRO could prove to be a time-saving nursery practice, yielding prime candidates for outplanting.
This study sought to develop effective protocols to root NRO stem cuttings at high frequencies and to examine the effects of several factors during rooting and subsequent containerized growth. Supplemental light and heat were administered to determine the effects of artificially extending the growing season of successfully rooted cuttings. Different container sizes were used to determine which size encouraged optimum containerized growth and survival. In addition, shoot production enhancement was studied through pruning of field grown stock seedlings so that stem cutting material could be readily available throughout the growing season; different seedling sources were used to examine provenance variability for shoot production. Also, early (ES) and late season (LS) cuttings were taken to determine the viability of rooting at different times during the growing season. After two seasons of containerized growth, final measurements of NRO rooted cuttings were recorded to determine efficacy of prior treatments.
Geographic source and prune height treatments were both found to have significant impact on the number of new shoots generated by NRO stock plants. We found large stem caliper may enhance donor plant ability to generate new shoots for rooting as compared to small stem caliper. Geographic source and prune height treatment significantly affected rooting ability of ES cuttings, which rooted at 64% overall. Rooting percentages were lower for LS stem cuttings (53% overall), but showed the possibility of LS rooting for nursery operations; prune height alone was statistically significant for rooting ability of LS cuttings.
During the first growing season, both growing environment and container size were significant in encouraging shoot growth post-rooting. After the first growing season and subsequent overwintering, survival rates of rooted cuttings were 75% overall. In this study, the smallest container size used during the first growing season was the most beneficial to rooted cutting growth based on final attribute measurements of height, root collar diameter (RCD), root mass, shoot mass, and root-to-shoot ratio, all of which have been proposed to be good indicators of field performance. Extending the growing season immediately after rooting significantly affected RCD and root mass measurements as well.